1. Field
Example embodiments relate to a restrainer bracket including a wedge and in particular a restrainer bracket for a jet pump assembly.
2. Description of the Related Art
Conventional boiling water reactors include a reactor pressure vessel (RPV) which surrounds a core shroud. The core shroud, in turn, surrounds a reactor core. Generally, each of the core shroud and the reactor pressure vessel are cylindrically shaped such that an outer diameter of the core shroud is less than an inner diameter of the reactor pressure vessel. Between a reactor pressure vessel wall and a core shroud wall is an annular space in which jet pump assemblies are typically located.
FIG. 1 illustrates a conventional jet pump assembly 25 located in the aforementioned annulus. As illustrated in FIG. 1, an inlet nozzle 10 extending through a sidewall 15 of the RPV 20, is coupled to the jet jump assembly 25. The jet pump assembly 25 includes a riser pipe 30 that extends between the shroud 35 and the sidewall 15 of the RPV 20. The riser pipe 30 is coupled to two jet pumps 35A and 35B by a transition assembly 40. Each jet pump 35A and 35B includes a jet pump nozzle 42, a suction inlet 45, an inlet mixer, and a diffuser 55. For example, the first jet pump 35A includes a first inlet mixer 50A and the second jet pump 35B includes second inlet mixer 50B. The jet pump nozzles 42 are positioned in the suction inlets 45 that are located at a first end of inlet mixers 50A and 50B. The diffusers 55, are coupled to a second end of inlet mixers 50A and 50B by a slip joint 65. Typically, both of the inlet mixers 50A and 50B and the diffusers 55 are formed of multiple cylindrical sections. Circumferential welds 70 join the cylindrical sections together.
A support member (riser brace) 75 typically surrounds the riser pipe 30 and connects to the riser pipe 30 via a weld 80 which may span approximately 180 degrees around the circumference of the riser pipe 30. The inlet mixers 50A and 50B are secured to the riser pipe 30 via a restrainer bracket 100.
Referring to FIG. 2, the conventional restrainer bracket 100 includes a first yolk-like member 105 surrounding the inlet mixer 50A. Though not shown, a similar yolk-like member surrounds mixer 50B. Because the yolk-like member surrounding the mixer 50B may be substantially the same as the yolk-like member 105 surrounding mixer 50A, only the yolk-like member 105 and its associated components will be described.
As shown in FIG. 2, the yolk-like member 105 surrounds the inlet mixer 50A. Penetrating the yolk-like member 105 are at least two set screws 110 which press against the inlet mixer 50A. In FIG. 2, only one set screw 110 is shown. A main wedge 115 is typically provided between a restrainer bracket pad 145 of the yolk-like member 105 and the inlet mixer 50A. The main wedge 115 includes a circular hole 190 (see FIGS. 3, 4, and 5) through which a wedge rod 130 passes. The wedge rod 130 has a threaded top end 131 which connects to an upper support casting 120 and a threaded bottom end which connects to a lower support casting 125.
The upper support casting 120 is arranged above the yolk-like member 105. The upper support casting 120 includes two vertically oriented plates 121 and 122 welded to the inlet mixer 50A. The vertically oriented plates 121 and 122 may be separated from each other by a distance d1 and may be parallel to each other as shown in FIG. 2. The upper support casting 120 also includes a third beam 123 which connects the middle portions of the two vertically oriented plates 121 and 122. The upper support casting 120 also includes a fourth plate 124 near top portions of the vertically oriented plates 121 and 122. As shown in FIG. 2, the fourth plate 124 is connected to inside faces of the vertically oriented plates 121 and 122. The fourth plate 124 is oriented horizontally and includes a hole through which the threaded top end 131 of the wedge rod 130 passes. A top surface of the fourth plate 124 may act as a bearing surface to support a nut 135 which may be configured to engage the threads of the threaded top end 131 of the wedge rod 130.
The lower support casting 125 is arranged below the yolk-like member 105. The lower support casting 125 includes two vertically oriented plates 126 and 127 welded to the inlet mixer 50A. The vertically oriented plates 126 and 127 are separated from each other by a distance d2 and are parallel to each other as shown in FIG. 2. The lower support casting 125 also includes a seventh plate 128 near bottom portions of the vertically oriented plates 126 and 127. The seventh plate 128 is oriented horizontally and includes a hole through which the threaded bottom end of the wedge rod 130 passes. As shown in FIG. 2, the seventh plate 128 connects to inside faces of the vertically oriented plates 126 and 127. A bottom surface of the seventh plate 128 acts as a bearing surface to contact a nut 140 which may be configured to engage the threads of the threaded bottom end of the wedge rod 130.
As shown in FIGS. 3 and 4, the conventional main wedge 115 is comprised of three portions: a head 150, a neck 155, and a body 160. The head 150 resembles a relatively thick horizontal plate having rounded edges and corners. The body resembles a wedge having an inclined face 156 (see FIG. 3), which engages the restrainer bracket pad 145 of the restrainer bracket 100. Widths d3, d4, and d5 (see FIG. 2) of the head 150, the neck 155, and the body 160 may be smaller than the distance d1 separating the vertical plates 121 and 122 and the distance d2 separating the vertical plates 126 and 127.
As previously mentioned, a hole 190 passes through the main wedge 115. The hole 190 is circular and extends through the head 150, the neck 155, and the body 160. The diameter D2 of the hole 190 is slightly larger than the diameter D1 of the wedge rod 130 to accommodate the wedge rod 130.
In the conventional art, the hole 190 penetrates the head 150, the neck 155, and the body 160. At a top surface of the head 150, however, the hole is chamfered creating a sloped surface 192 to allow the wedge rod 130 to be easily inserted into the head 150. Likewise, at a bottom surface of the body 160 the hole 190 is chamfered creating another sloped surface 194.
In the conventional art, because the diameter D2 of the hole 190 of the wedge 115 is larger than the diameter D1 of the wedge rod 130, the wedge 115 is free to slide along the wedge rod 130.
FIG. 5 is a cross-section of the main wedge 115 of the conventional restrainer bracket 100 and FIG. 6 is a cross-section of the main wedge 115 with the wedge rod 130 in the hole 190. As shown in FIG. 6, the main wedge 115 may be slightly inclined with respect to the wedge rod 130. Therefore, corners A+ and B+ of the chamfered areas 192 and 194 of the head 150 and the body 160 may contact the wedge rod 130.